At present, a communication system architecture including Baseband building Units (BBUs) and Remote Radio Units (RRUs) is deployed in a Third-Generation (3G) mobile communication network, where the BBUs are connected with the RRUs over optic fibers, and one BBU can support a number of RRUs.
FIG. 1 illustrates a schematic architectural diagram of a communication system including BBUs and RRUs, where a BBU is connected with an optical interface of an RRU over an optic fiber, the optical interface in the RRU is connected with a digital intermediate-frequency component, and the digital intermediate-frequency component is connected respectively with an array of transceivers, and a transmission and reception calibrating unit. Here the transceivers are connected with an array of Power Amplifiers (PAs) and Low Noise Amplifiers (LNAs), the array of PAs and LNAs is connected with an array of passive antenna, and the transmission and reception calibrating unit is connected with the array of passive antennas over a calibration radio frequency channel. As can be apparent, the RRU is connected with the passive antennas through (N+1) radio frequency jump-up lines, the number of which increases with the increasing number N of antenna radio frequency channels.
In a massive Multiple-Input Multiple-Output (MIMO) communication system, the number N of antenna radio frequency channels is more than or equal to 64, that is, the number of radio frequency jump-up lines is more than 64, and in order to alleviate a transmission loss between the antennas and the RRU, the jump-up lines are typically radio frequency cables with certain diameter, but it is rather difficult to engineer a large number of radio frequency cables, and to guarantee the reliability thereof.
Accordingly the existing solution to the communication system including the BBUs and the RRUs together with the passive antennas is not feasible in the massive MIMO communication system.